The thermoplastic resin product, particularly polyethylene terephthalate product, has been utilized especially for containers for various applications since it is free from toxicity, superior in gas-barrier ability and water-impermeability to other synthetic resins and having an exterior appearance similar to that of glass, and the like. Such applications include containers for cosmetics and toiletries, liquid seasonings, drinks such as beer or cola, medicine, detergents, and the like. In many cases, explanatory notes and trade names have been printed on the side wall of the container body with the printing ink made from ultraviolet-curable type resin as a vehicle.
In recent years, the environment has been a matter of worldwide concern, and industrial waste, in particular, the discharge of industrial products in a large scale, has attracted public attention, which requires an urgent countermeasure for its reduction. Covering a certain industrial product such as a metal product and glass product etc., collection of used product has commenced and while it is somewhat imperfect yet, the volume of discharge has now been decreased.
However, the recovery system has not been applied to any plastic products partly because most of them are combustible. This is attributable to the fact that the various types of plastic products are discarded as lump-sum "plastic" since it is difficult to classify many plastic products by their types. In cases where the plastic is classified by its type and collected in groups of each type separately, it my be utilized as a secondary product upon processing for regeneration so that loss of thermal energy in incineration as well as pollution of the atmosphere with CO.sub.2 gas can be prevented. Thereby, a greater contribution may be expected in cleaning the environment on the earth.
Plastics, especially the reproducible thermoplastic resins, are the industrial products that have a merit in the recovery. But many plastic products contain various additives depending upon application purposes and end-usage, and the composition is not always uniform even if classified in the same resin category.
Among them, plastic containers have a relatively stable composition even though they contain some quantity of additives to prevent deterioration in the quality of the contents, which makes the approach to the regeneration easier. The container made of polyethylene terephthalate, in particular, is utilized as a transparent container for drinks on a big scale and the early realization of the system for its collection and regeneration stands a better chance as one of the promising products to be collected in a route reverse to that of sales channel similar to glass bottles.
One obstacle in the collection and regeneration is the decoration, i.e. labeling or printing of marks, figures, explanatory notes and the like on the container to display trading image. An immediate task is how to conduct a lump-sum removal of the decorative portions without any sorting work after their collection to restore an original shape to the container materials.